DESCRIPTION (Taken from application) Many environments contain polycyclic aromatic hydrocarbons (PAHs) and N-heterocyclic aromatics (NHAs) as complex mixtures. Specifically, 3000 former sites of coal gasification plants containing PAHs and NHAs constitute major health hazards in the U.S. The overall objective is to enhance the biodegradation and mineralization of mixtures of PAHs for the elimination of PAHs and their metabolites from polluted soils containing metals and PAHs. This proposal targets the recalcitrant, carcinogenic 4 and 5 ring PAHs and NHAs and mixtures in these soils. The focus is to characterize the biochemical and genetic basis of PAH degradation pathways in bacteria and determine the effects of complex mixtures of PAHs and metals on these degradation pathways. Therefore, the specific aims are to: 1) determine the biodegradation pattern of PAH mixtures relative to individual PAHs and the impact of metals on bacterial biodegradation; 2) determine the ability of 4 and 5 ring PAH degraders(and 3-5 ring NHA degraders) to perform the limiting step in metabolism for soil microorganisms; 3) identify and characterize the genetic basis for high molecular weight PAH (and NHA) degradation. This research will involve determining the metabolism and mineralization rates, metabolic intermediates, reaction sequences and accumulation of reaction products by HPLC/MS/fluorescence. The ability of algae to initially metabolize mixtures, and low molecular weight degraders and soil microorganisms to degrade partially metabolized PAH mixtures will be determined by HPLC/MS/fluorescence. PAH degradative genes for high molecular weight degraders will be identified and characterized and the functionality and sequence relatedness to other known genes will be determined. Lastly, the occurrence and distribution of PAH degradative genes in soil populations will be determined using PCR primers based on sequence information. With an understanding of the microbial hydrocarbon degradation process, strategies will be developed to enhance the removal of PAHs, NHAs and their intermediates from contaminated soils.